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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything. When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action. For a problem as potentially catastrophic as climate change, taking no action poses a dangerous risk for our planet...

... The Intergovernmental Panel on Climate Change (IPCC) and other scientific assessments of climate change, which involve thousands of scientists producing massive and comprehensive reports, have, quite expectedly and normally, made some mistakes. When errors are pointed out, they are corrected. But there is nothing remotely identified in the recent events that changes the fundamental conclusions about climate change:

The planet is warming due to increased concentrations of heat-trapping gases in our atmosphere. A snowy winter in Washington does not alter this fact.

Most of the increase in the concentration of these gases over the last century is due to human activities, especially the burning of fossil fuels and deforestation.

Natural causes always play a role in changing Earth's climate, but are now being overwhelmed by human-induced changes.

Warming the planet will cause many other climatic patterns to change at speeds unprecedented in modern times, including increasing rates of sea-level rise and alterations in the hydrologic cycle. Rising concentrations of carbon dioxide are making the oceans more acidic.

The combination of these complex climate changes threatens coastal communities and cities, our food and water supplies, marine and freshwater ecosystems, forests, high mountain environments, and far more.

Much more can be, and has been, said by the world's scientific societies, national academies, and individuals, but these conclusions should be enough to indicate why scientists are concerned about what future generations will face from business-as-usual practices. We urge our policy-makers and the public to move forward immediately to address the causes of climate change, including the un restrained burning of fossil fuels.

It is hard to get 255 members of the U.S. National Academy of Sciences to agree on pretty much anything, making the import of this letter even more substantial. Moreover, only a small fraction of National Academy members were asked to sign (the signatories are all members of the U.S. National Academy of Sciences but were not speaking on its behalf). Because of a desire to produce a statement quickly, the coordinators of the letter focused on those sections of the NAS most familiar with climate science and the ongoing debate. But the NAS (and Academies of Sciences and other professional scientific societies from dozens of other nations) has previously published a long set of assessments and reviews of the science of climate change, which support the conclusions laid out in the Science essay.

Comments

Let me be the first to respond to this august panel (my compliments to anyone who sits through 4-12 years of science to earn a degree of any kind)
1. **** NO, but a decade of snowy winters in Alaska, Washington, Russia and most of western Europe make a statement towards declining temperatures.

2. ***( deforestation surely plays a role, however since many of the farms which stole trees from the South American Rain forests are now growing back in exponential numbers we should see some leveling in that region. Also again CO2 is known to be the 5th least effective of the greenhouse gases and there have been points where it was 7000 to 14000ppm compared to the paultry 385ppm today. Where is the emergency? The earth is still here and has levelled out numerous times.
It has been proven numerous times that when you look at things over a million to 10 million year period, it is very obvious that carbon levels follow temperature levels so again what is the emergency?

3. Again at numerous times in earth history the co2 ppm levels have been 18 to 36 x's higher than they are now so, which natural forces are being overpowered by human interevention.
At times when the equator was a sludge pot so hot you'd boil just getting into the water the co2 levels were lower than they are today, there have been an ice age or two where the co2 levels are higher than they are today and there have been times with similar temperatures where the co2 levels were 18x's higher than they are now. Once again there is a statement of previous times natural forces being affected by man's activities but no scientific evidence to back this up.

4. Where are the studies that say the oceans are becoming more acidic in nature? I have not seen one.
Throw into this again the fact that combined NASA and Remote Sensing Systems study showing oceanic temperatures are showing global oceanic cooling over the last 10-20 years. Are we absolutely positively sure beyond a 100% shadow of a doubt that any possible acidity levels have not been caused by volcanic effluence beneath the oceans surface? I have not seen any exhaustive studies on either side of this comment.

skepticstudent - if you want to be taken seriously here, please supply references and refrain from logical fallacies.

Would you care to provide a reference for your claim that winters in Alaska, Washington, Russia, and western Europe have been snowier, as well as evidence that snowier = colder?

Also, just because CO2 has followed initial temperature rise over the ice core record, that doesn't mean it's doing so now. This is referred to as a "predictive appeal to history" fallacy, and it's something I addressed here.

In fact, given that deglaciations take thousands of years, scientists currently hypothesize that a CO2 feedback in response to a small initial change in insolation is what drives the ultimate transition from a glacial period to an interglacial (Source).

Again, there is no scientific evidence to date that shows any horrendous raising of coastal water. I believe the IPCC worst estimate brought forth in any of the 1-4 assessments was a raising of about 1 foot globally. Where is the catastrophe in a one foot rise in oceanic levels. The seas have risen and lowered far more drastically than that through the ages. If there is any question, I can take you to places in Alaska where ancient natives wrote in rock that is now under water and then other ancients that wrote on rocks which is now dozens of feet from shoreline even at highest of tides. The importance to note is this is at a known native Alaskan fishing village which is over 2000 years old or older.
Another good example is Lake Shasta, California. My grandfather grew up there in the latter half of the 19th century. The town he grew up in was flooded and covered by water for 45 years because of heavy rainfall for several decades. It is now uncovered again.

@skepticstudent... I think you need to step back for just a moment and challenge yourself and your own grasp of the subject matter. We are talking about 255 members of the NAS. These are not your run-of-the-mill PhD's. These are some of the finest minds in the world, and these are also the members of the NAS who are most familiar with climate science. They know of what they speak.

One needs to ponder the significance of the statements these people are making. These are NOT willy-nilly assertions. They are making very definitive statements about the state of climate science and the predicament humanity faces.

robhon
I gave them the respect they deserve.
Whether I agree with them or not does not mean I don't respect the hours, sweat, and time away from family any scientist puts into their scientific degree.

However, and I mean this with all due respect... Einstein was laughed out of numerous houses of academia because he had not proven his theory of relativity. He went from one to another with the same results. If I were around at the time of Einstein, I would have told him the same thing I am saying today, just because you say the same thing over and over based on previous results doesn't make it any more right this time than the previous times. It doesn't make it any more valid when you have a bunch of well respected scientist saying the same thing that less experienced scientists say.

Response: Just for the record, I did email skepticstudent suggesting he post shorter comments on specific scientific topics and he has been doing that. I would also suggest to skepticstudent that you do a quick search before commenting as many of the topics you do raise are covered in detail elsewhere on this site and a quick search will find them easily.

Lest we forget: it took 80 years for the evidence of pre-Cambrian fauna to be accepted. Ironically, Nature magazine rejected one of the most compelling proofs, as it was presented by a "nobody", only to change their mind when finally a renowned scientist bothered to check things out. So much for peer-review and consensus science.

Tom,
I was responding to the topics as presented by the paper in this thread. Which is why I numbered each of my statements to match the numbered statement in the release.
I am new to this blog and I don't know where all the threads are yet, however I was very much on track as I was responding directly to the topics as numbered in the paper.

skepticstudent, in the left margin, near the top, of every page there is a list of "Most Used Skeptic Arguments." At the bottom of that list there is a "View All Arguments" link that leads to a descriptive list with links to all the arguments that have posts.

To Mr. Cook and everyone else. I just went and read the comments about previous global temperatures and co2 levels. They seem to be right on with what I've been saying both in response to this paper at the top of this thread. The only thing I would have to check from both sides is whether or not during the medevil warming period what the levels of sun activity was. I believe there have been some newer research showing that at times in the past when sunspots were higher the temperatures were similar to what they are today.

However I digress. That comment that Mr Cook was nice enough to link me too pretty much denies that any manmade activity could cause disastrous results because the carbon levels in the past were not caused by man.

I'm just making this reference here because it was linked to this thread based on my earlier response to this paper.

In response to angliss at 08:55 AM on 8 May, 2010
skepticstudent - if you want to be taken seriously here, please supply references and refrain from logical fallacies.

Would you care to provide a reference for your claim that winters in Alaska, Washington, Russia, and western Europe have been snowier, as well as evidence that snowier = colder?

I will reference the tracked temperatures of the US Weather beareau and the fact that I lived in Alaska in 2008 and it was colder than the previous year etc etc.
Snow has typically been known (since I took science in 6th grade) to mean a given point in time that temperatures are colder. It doesn't snow in summer, ergo winter is colder than summer.

Given the temperatures of Alaska, Russia and several other places, it would be a reasonable conclusion that my statements were not baseless. It has been suggested to me that my comments be made shorter so I won't go further than that.

As I mentioned yesterday in a post that needs to be re-written end of calendar year 2007 beginning of 2008, Alaska, Canada and Arctic Ice in general saw a tremendous increase in ice levels.
2008 had the 3rd coldest winter since thermometers were created in 1775. Temperatures have been continuously declining since 1999.
The main reason for the tremendous increase in Arctic ice was accounting to heavier than normal windstorms causing the snow to not stay in one spot as is typical. As we all know, eskimo's build igloos as the snow acts as insulation.
Having said that, because there was far much less snow insulating the ground there was a tremendous amount of ice growth in the arctic.
I would like to know what logical fallacy I threw out by the way.

To Tom and John, I believe it was fair of me to enter my comments here. If the 5 points of the NAS paper have been addressed in other threads, I think it is fair to address them here as they are being brought up here.
I don't think it could be fairly construed as off topic when the topic of the thread IS the paper.
With all due respect.

00

Response: A fair point which is why the comments stand (and I appreciate you taking my suggestion of shorter, more specific comments). I would still recommend doing a quick search before commenting in the chance that you're bringing up a point that has been examined elsewhere - at least so you can see what is being discussed elsewhere.

skepticstudent, one way to comment on cross-post topics is to add your substantive comment to the post that is devoted to that topic (e.g., "It’s the Sun" and the other posts that John Cook and others have pointed you to), and then add a short comment to the multi-topic post (such as this one) with a link to your comment on the other thread saying "I've commented in more detail on the thread X." You can link to your comment by right-clicking on the comment's time-date, copying the link, then pasting it into your shorter comment within the appropriate HTML tags.

A major reason for commenting in the appropriately specialized post, is that the post and the existing comments probably address your concern. By reading those first you can hone your comment to more effectively get the answer you desire or to spark the discussion you hope to start.

Another reason to stick to the appropriately specialized post is to avoid diluting the discussion of the broader post.

"That comment that Mr Cook was nice enough to link me too pretty much denies that any manmade activity could cause disastrous results because the carbon levels in the past were not caused by man."

Man can cause a disaster by starting a fire in a forest even though forest fires in the past were not caused by man. The cause has no relevance as to whether the result is disastrous.

Homo Sapiens didn't exist last time co2 was as high as it is today. So this is the first time that cities and agriculture is going to be tested against raising co2 levels. As a result there's no way we can rule out disasters occurring to human civilization.

It's also not so much the carbon levels, but how fast they change. All species, including us, are going to find it easier to adapt to slowly changing conditions than fast changing conditions.

Skeptic student,
You are clogging up this site with repetative ranting. You are uninformed about the temperatures that have been measured. As was pointed out to you on another thread, 2008 was the 10th warmest year measured since the thermometer record started, not the 3rd coldest. (reference NCDC and GISS). Many of your other assertions are covered on this site. If you cannot get the basics right you need to inform yourself before you continue your ranting.

Since you seem to have wide-ranging interests, you probably would enjoy the broad but fairly short overview The Global Warming Debate. It will also save you a lot of time by orienting you to better take advantage of this Skeptical Science site's detailed info on specific topics.

>NO, but a decade of snowy winters in Alaska, Washington, Russia and most of western Europe make a statement towards declining temperatures

Even if we assume this is accurate, the logical fallacy here is the idea that regional trends are the same as global trends. They are not. Take a look at the posts on this site that discuss global temperature trends, especially that of ocean temperatures.

>the fact that I lived in Alaska in 2008 and it was colder than the previous year

This is similar to the above fallacy but on a temporal scale. Year-to-year changes do not reveal long term trends. You need to look at long term (10+) year averages on a global scale. Please take some time to try and understand what constitutes a long-term global trend.

"Snow has typically been known (since I took science in 6th grade) to mean a given point in time that temperatures are colder."

The temperatures may be colder but that's no guarantee of snowfall. The majority of snow falls when the temperatures are -9C (15F) or warmer. See All About Snow. So therefore depending upon conditions it is totally possible for there to be more snowfall in a warmer climate than a colder one. There is a fairly good elementary discussion here.

i'm responding to this here because the insulting comments were aimed at me here.
michael sweet at 11:10 AM on 8 May, 2010
Skeptic student,
You are clogging up this site with repetative ranting. You are uninformed about the temperatures that have been measured. As was pointed out to you on another thread, 2008 was the 10th warmest year measured since the thermometer record started, not the 3rd coldest. (reference NCDC and GISS). Many of your other assertions are covered on this site. If you cannot get the basics right you need to inform yourself before you continue your ranting.

Before you start insulting people, you might want to take another look at peer reviewed papers on the debaucle known as the weather data for october 2008. The information from the NCDC and Giss has been called into question because it was a major anomoly. The temperature information from the GISS output was proven wrong for at least October 2008. The temperatures given by the GISS were in error and after investigation, it was found that GISS was given the temp readings for September so the readings for October were based on incorrect readings. The actual correct temperatures were shown to be the 70th warmest season since 1775.
I will be responding to NCDC temperature readings in another post when I have time. If you had really read what I had said you would have seen that I stated the temperatures have been declining for the last 20 years, I think that meets your qualification for 10+.

Your comments to regionalism is one of the main contentions of the side of the skeptics that we aren't even talking about global warming trends we are talking about a few regions. But I won't make my comment any lengthier than it already is to discuss things already mentioned.

>the fact that I lived in Alaska in 2008 and it was colder than the previous year

Skepticalstudent needs to grasp the very simple difference between *climate* and *weather*. Here in Australia, we've had going on *6 months* of above average temperatures-with November 2009 recording some of the highest temperatures seen since records were first kept. Now, in spite of my leanings on this issue, I'm not going to turn around & claim that this is *proof* of global warming-because its not (well, not on its own anyway). What *is* proof of global warming is the 30 year warming trend-from 1979-2009-occurring in spite of a decline in Total Solar Irradiance over a similar period. So to is the long-term (i.e. decades) decline in glaciers & ice-caps.

Ron, I think I have a pretty good grasp on temperatures and snow fall since I've lived in the Pacific Northwest for over 30 years and I have lived in Alaska.

Ron, you are totally 100% correct, I will not dispute with you on your statements. The only reason why I mentioned that was earlier someone asked me what snowiness had to do with coldness. The warmest I've ever seen snow occuring in at less than 1000 ft elevation was around 36F.

The whole point was to go into the information about the windstorms and blowing snow drifts and the faster than normal buildup of ice in 2008.
There is a fascinating read on the fabled inland passage which was actually open in 2007 and closed again by a massive and quick buildup of ice in the Arctic in early 2008.

There have been several scientific papers written on this and even one of the global warming faithful tried to take a kayak with two ships of camera crew and journalist behind him but he was turned back by a vast amount of unexpected ice which had grown in less than a year. One would have to assume that if ice grows back that quickly, that much that it is fairly cold, not rising catastrophically.

If I have to pull out all the references to this I will but it's pretty well known.

Marcus you want to recheck your facts.
Even the NASA GISS facts don't dispute that the temperatures have been declining on a global basis since the year 2000. Agree with me or not the facts are there. so we'll just let this one go and agree to disagree.

e at 11:19 AM re "the logical fallacy here is the idea that regional trends are the same as global trends"
This is something I am somewhat sceptical about where proxies have been used to reconstruct historical global temperatures. How many of the proxies are tied to local temperatures, as they should be, and how many are tied to the global temperature.
I wonder just how available, or how reliable are local temperature records given that many proxies seem to be located in remote locations.
It is not something that is readily apparent when the research is being presented.

Tom your second point about commenting in another post then pointing a link from a post like this to that one not mottling the main topic is a good point.
I will endeavour to take that track in the future.

Marcus at 11:39 AM re What *is* proof of global warming is the 30 year warming trend-from 1979-2009-occurring in spite of a decline in Total Solar Irradiance over a similar period.
I would consider that the said warming trend was more so proof that the post WW2 30 year cooling trend had ended, similar as it had previously done so as indicated by the various natural cycles identified and traced back centuries, many of which are still not fully understood.

RE: Riccaro @#9
Yes, I'd bet that most would agree. However, NAS has over 2000 members. Even though only some sections were asked to sign, it would be more persuasive if we could say that 90%, say, of those requested did sign. The relative number (ie the percentage) of those signing is a more compelling statistic then the absolute number, in my opinion.

skepticstudent, there are data on snow cover over the entire northern hemisphere, which although less than global is hugely more than the tiny regions in which you have lived. Details in Tamino's post "Snow."

Too much noise here this time. Repetitive posting of discredited arguments does not stimulate any useful discussion.

Among the many fallacies presented here were a couple of comments about Alaska. Given that I live and work there, I'll respond to those.

(1) 2008 was indeed a miserable, wet, rainy cold summer. The worst in many years. So the obvious question is, what about 2009? It was nearly the opposite! Far warmer and nicer overall than 2008. Was it an incredible warming trend in 2008-2009? No, this is what we call weather, and to say anything about climate you need to average over a lot of years of weather.

(2) Along most of the southern coastline of Alaska, vertical motion of the land is much faster than the change in sea level. Some parts of southeast Alaska are rising faster than 30 mm/yr due to the rebound of the crust from melting ice. See Chris Larsen's website for a sampling of the results, if you don't want to track down the original papers. Along many parts of the Pacific coast from the Aleutians eastward, the land is subsiding due to the buildup of strain leading toward great thrust earthquakes at the Alaska subduction zone. Further inland, we find uplift (for example, along Cook Inlet) for the same tectonic causes. In many places the land level change, in either direction, is significantly faster than sea level change. So extreme changes in relative sea level in Alaska tell us nothing about global sea level rise or climate.

Nearly all your claims run counter to the bulk of mainstream peer-reviewed scientific literature, as you can see linked to profusely on this site. So, yes, you will need to provide some reliable references to back your claims.

Now back to the original topic? The letter is a fine letter, and as a scientist I would be proud to sign it myself. If there is a supporting petitition, I'll gladly add my name, whether such things count for anything or not. I found it right on the money.

I particularly liked the sentence, "Even as these are overwhelmingly accepted by the scientific community, fame still awaits anyone who could show these theories to be wrong." [referring to the age of the Earth and the age of the universe]. That's absolutely correct.

Jeff Freymueller at 12:28 PM, can any of the rising parts of land be associated with subsidence elsewhere, or the reverse? Only some materials would be compressible but even those would require something to be drawn into their structure as the pressure reduced.

"One would have to assume that if ice grows back that quickly, that much that it is fairly cold, not rising catastrophically."

I'm not sure what you mean at the end of this statement, but as far as cold temperatures and sea ice growth are concerned. There is much more that has to be taken into consideration than the temperatures on their own. You need to also take into consideration such factors as ocean currents and atmospheric pressures in order to make any definitive conclusions surrounding sea ice growth. The analysis of conditions posted at NSIDC on April 6, 2010 illustrates this very well.

Quote: "This March, low atmospheric pressure systems persisted over the Gulf of Alaska and north of Scandinavia. These pressure patterns led to unusually cold conditions and persistent northerly winds in the Bering and Barents Seas, which pushed the ice edge southward in these two regions."

but

Quote: "This winter's strong negative mode of the Arctic Oscillation was moderated through the month of March. Average air temperatures for the month nevertheless remained above average over the Arctic Ocean region. Overall for the winter, temperatures over most of the Arctic were above average, while northern Europe and Siberia were colder than usual.

and

Quote: "Ice extent was above normal in the Bering Sea and Baltic Sea, but remained below normal over much of the Atlantic sector of the Arctic, including the Baffin Bay, and the Canadian Maritime Provinces seaboard. Extent in other regions was near average.

and

Quote: "The late date of the maximum extent, though of special interest this year, is unlikely to have an impact on summer ice extent. The ice that formed late in the season is thin, and will melt quickly when temperatures rise."

And the latter statement is being borne out if you look at the graph of current Arctic sea ice extent.

SkepticalStudent. Nice to see that you won't let the facts get in the way of a good story (I noted that, when against the wall, you resorted to ad hominem attacks again-the hallmark of someone whose position is incredibly weak) GISS shows a modest warming of 0.012 degrees for 2000-2009, in spite of that decade being dominated by a deep solar minimum (i.e. it *should* have cooled). Yet 10 years do not a trend make-because the results are statistically insignificant. 30-60 years of continuous data do provide the correct amount of statistical significance because the signal-to-noise ratio is much better, & all this data is showing a *strong* warming trend. BTW, I was never *taught* to be "alarmist". As a scientist I carefully reviewed *all* the scientific literature-both for & against-before I came to the conclusion that global warming was occurring, & that humans were the most obvious cause. Common sense also dictates my position on the issue-because I find it ludicrous that you can pump *millions of years* worth of geo-sequestered CO2 into the atmosphere, in the space of less than 200 years, & not expect it to have a measurable impact on the biosphere. When the basis for our oil & coal were being laid down, the planet's CO2 concentrations were 10x higher than today-& the planet was a good 6 degrees warmer than today too. Coincidence? I think not!

42Thank Jeff. That was pretty much my point, although I didn't word it as succintly as you. People are always making accusations without looking at certain regions on the globe which are acting totally different.
48. Marcus...6 degrees warmer... and yet today the earth is still spinning just like it was then isn't it.
So could it be that it is not so catastrophic and maybe more cyclical in natuer.
You can't have your cake and eat it to. And What was my ad hominem?
I couldn't find one.

Yes the Earth was still turning back then, but mammals weren't part of that Earth-& nor were most of the plants which make up the current biosphere (& on which the bulk of our agriculture relies). Life at that time had evolved-over millions of years-to thrive in a relatively high CO2/high temperature world. Similarly, the life which exists in the Quaternary Era has evolved, over millions of years, to thrive in a low-CO2/low temperature world. So what we're doing is setting the climate clock back to a time for which current life on Earth is not adapted-& in a period of decades to centuries-not millions of years as has happened previously. Previous "rapid" changes in climate-(on the order of centuries to millenia)-caused massive extinction events. To suggest that our actions now won't have a bad-if not worse-consequences for life on this planet (& human life in particular) represents the worst combination of arrogance & ignorance imaginable.
Oh & as for your ad hominem-it was claiming that everyone here has been "taught" to be alarmist & that apparently we can't think for yourself-& at the same time implying that somehow only people like you & Camel have access to the real *truth*! That constitutes ad hominem in my books, but fortunately it was since deleted from the site.